224 POISONS : THEIR EFFECTS AND DETECTION. [§ 277 . 
is usually so small at any given moment that no injury is caused ; but there are condi¬ 
tions in which it may kill speedily . 1 
Mercuric cyanide, it has been often said, acts precisely like mercuric chloride 
(corrosive sublimate), and a poisonous action is attributed to it not traceable to 
cyanogen; but this is erroneous teaching. Bernard 2 declares that it is decom¬ 
posed by the gastric juice, and hydric cyanide set free; while Pelikan puts it in the 
same series as amnionic and potassic cyanides. Lastly, Tolmatscheff , 3 by direct 
experiment, has found its action to resemble closely that of hydric cyanide . 4 
Silver cyanide acts, according to the experiments of Nunneley, also like hydric 
cyanide, but very much weaker. 
Hydric sulphocyanide in very large doses is poisonous. 
Potassic sulphocyanide, according to Dubreuil and Lcgros , 5 if subcutaneously 
injected, causes first local paralysis of the muscles, and, later, convulsions. 
Cyanogen chloride (CNC1) and also the compound (C 3 N 3 C1 3 )—the one a liquid, 
boiling at 15°, the other a solid, which may be obtained in crystals—are both 
poisonous, acting like hydric cyanide. 
Cyanogen iodide (CNI), according to Robert, is four times weaker than prussic 
acid, but it is a powerful poison for unicellular organisms. The nitriles have but 
slight toxic action. Aceto-nitrile is a good medium for bacterial growth. The iso- 
nitriles, on the contrary, are powerful poisons. 
Methyl cyanide is a liquid obtained by distillation of a mixture of calcic methyl 
sulphate and potassic cyanide. It boils at 77°, and is intensely poisonous. Eulen- 
berg 6 has made several experiments on pigeons with this substance. One example 
will suffice :—A young pigeon was placed under a glass shade, into which methyl 
cyanide vapour, developed from calcic methyl sulphate and potassic cyanide, was 
admitted. The pigeon immediately became restless, and the fseces were expelled. 
In forty seconds it was slightly convulsed, and was removed after a few minutes’ 
exposure. The pupils were then observed not to be dilated, but the respiration had 
ceased ; the legs were feebly twitching ; the heart still beat, but irregularly ; a turbid 
white fluid dropped out of the beak, and after six minutes life was extinct. 
The pathological appearances were as follows :—In the beak much watery fluid ; 
the membranes covering the brain weakly injected ; the plexus venosus spinalis 
strongly injected ; in the region of the cervical vertebra a small extravasation between 
the dura mater and the bone ; the right lung of a clear cherry-red colour, and the 
1 The presence of ferro-cyanide is easily detected. The liquid is, if. necessary, 
filtered and then acidified with hydrochloric acid and a few drops of ferric chloride 
added ; if the liquid contains ferro-cyanide, there is immediate production of Prussian 
blue. It may happen that potassic or sodic cyanide has been taken as well as ferro- 
cyanide, and it will be necessary then to devise a process by which only the prussic 
acid from the simple cyanide is distilled over. According to Autenrieth, if sodium 
hydrocarbonate is added to the liquid in sufficient quantity and the liquid distilled, 
the hydric cyanide that comes over is derived wholly from the sodium or potassium 
cyanide. Should mercury cyanide and ferro-cyanide be taken together, then this 
process requires modification ; bicarbonate of soda is added as before, and then a 
few c.c. of water saturated with hydric sulphide ; under these circumstances, only 
the hydric cyanide derived from the mercury cyanide distils over. If the bicarbonate 
of soda is omitted, the distillate contains hydric cyanide derived from the ferro- 
cyanide. 
2 Substances Toxines, pp. 66-103. 
3 “ Einige Bemerkungen fiber die Wirkung von Cyanquecksilber,” in Hoppe- 
Seyler’s Med. Chem. Untersuchungen, 2 . Heft, p. 279. 
4 Mercury cyanide may bo detected in a liquid after acidifying with tartaric acid, 
and adding a few c.c. of SH 2 water and then distilling. S. Lopes suggests another 
process : the liquid is acidified with tartaric acid, ammonium chloride added in 
excess, and the liquid is distilled. A double chloride of ammonium and mercury is 
formed, and HCN distils over with the steam.— J. Pharm., xxvii. 550-553. 
Compt. Rend., lxiv. 561, 1867. e Oewerbe Hygiene, p. 392. 
